Linear fresnel optic for reducing angular spread of light from led array

ABSTRACT

A light source may comprise a cylindrical lens, for example a cylindrical Fresnel lens, a linear array of light-emitting elements, the linear array aligned with and emitting light through the cylindrical Fresnel lens, wherein the cylindrical Fresnel lens reduces the angular spread of light in a widthwise axis of the linear array, the linear array spanning a lens length.

RELATED APPLICATIONS

The present application claims priority to U.S. Patent Application No.61/624,974, filed on Apr. 16, 2012, the entire contents of which arehereby incorporated by reference for all purposes.

BACKGROUND AND SUMMARY

Ultraviolet light sources, such as mercury arc lamps and solid-state UVlight sources comprising arrays of light-emitting diodes (LEDs) arecommonly used for curing in coatings, inks, and adhesives in theimaging, printing, and telecommunication industries. LED technology isreplacing traditional mercury arc lamps because they are more energyefficient, last longer, have lower operating temperatures, are safer andmore environmentally friendly to use, can be manufactured morecompactly, among other reasons.

LEDs and other types of light sources may be characterized as exhibitinga Lambertian or near-Lambertian emission pattern. Accordingly, onechallenge with UV curing is providing a uniform irradiance of lightacross an entire target object or surface. In particular, curing oflarge two-dimensional surfaces may require manufacture of large lightsources that are costly and cumbersome, or may require combiningmultiple light sources to provide irradiance over the target surfacearea. The inventor herein has recognized a potential issue with theabove approaches. Namely, irradiance uniformity may be poor, especiallynear edges of emission patterns of individual light sources and atjunctions between multiple light sources.

One approach that addresses the aforementioned issues includes a lightsource comprising a cylindrical lens, for example a cylindrical Fresnellens, and a linear array of light-emitting elements aligned with andemitting light through the cylindrical Fresnel lens, wherein thecylindrical Fresnel lens reduces the angular spread of light in awidthwise axis of the linear array, the linear array spanning a lenslength. Furthermore, the light source may comprise a housing, wherein awindow may be mounted in a front plane of the housing, the window lengthspanning a front plane length, and wherein first and last light-emittingelements of the linear array are positioned adjacent to widthwise edgesof the window, and wherein window sidewalls at the widthwise edges arealigned flush with the housing sidewalls. In this manner, emissionpattern uniformity of the light source can be enhanced for an individuallight source and across multiple light sources as compared toconventional light sources.

It will be understood that the summary above is provided to introduce insimplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a near-Lambertian emission pattern.

FIG. 2 is a schematic of an example of a regularly spaced linear arrayof light-emitting elements.

FIG. 3 is a schematic illustrating an irradiance pattern for theregularly spaced linear array of light-emitting elements of FIG. 2.

FIG. 4 is a plot showing a cross section of the irradiance pattern ofFIG. 3.

FIG. 5 is a schematic of an example of a linear array of light-emittingelements with edge weighted spacing.

FIG. 6 is a schematic illustrating an irradiance pattern for the edgeweighted linear array of light-emitting elements of FIG. 5.

FIG. 7 is a plot showing a cross section of the irradiance pattern ofFIG. 6.

FIG. 8 is a plot of the irradiance profiles of FIG. 4 and FIG. 7.

FIG. 9 is a plot of the irradiance profiles of FIG. 4 and FIG. 7, and aplot of the irradiance profile of an edge weighted linear array withinterior lensed LEDs.

FIG. 10 is a frontal view of an example light source.

FIG. 11 is a partial frontal view of two of the example light sources ofFIG. 10 positioned side by side.

FIG. 12 is a partial side perspective view of the example light sourceof FIG. 10.

FIG. 13 is a frontal perspective view of the example light source ofFIG. 10.

FIG. 14 is a schematic illustrating an example of a lighting system.

FIG. 15 is an example flow chart for a method of using a light source.

FIGS. 16A and 16C are perspective views of example cylindrical Fresnellenses.

FIGS. 16 B and 16D are cross-sections of the example cylindrical Fresnellenses of 16A and 16C, respectively.

FIG. 17 is a partial side perspective view of an example light sourcewith a cylindrical Fresnel lens.

FIG. 18 is a cross-section of an example double cylindrical Fresnellens.

DETAILED DESCRIPTION

The present description relates to a light source, method of using alight source, and lighting system for use in manufacture of coatings,inks, adhesives, and other curable workpieces. FIG. 1 illustrates anexample of a near-Lambertian emission pattern for an LED light-emittingelement. FIG. 2 shows a schematic depicting an example of a linear arrayof light-emitting elements arranged in a regularly spaced manner. FIGS.3 and 4 illustrate an example of an irradiance pattern and across-sectional plot of the irradiance pattern for the regularly spacedlinear array of light-emitting elements in FIG. 2. FIG. 5 shows aschematic depicting an example of a linear array of light-emittingelements, wherein the light-emitting elements are distributed with edgeweighted spacing. FIGS. 6 and 7 illustrate examples of an irradiancepattern and a cross-sectional plot of the irradiance pattern for theedge weighted linear array of light-emitting elements in FIG. 5. FIGS. 8and 9 are plots comparing the example irradiance profiles of FIGS. 4 and7, and comparing the example irradiance profiles FIGS. 4 and 7 and thatof edge weighted linear array with interior lensed LEDs. FIG. 10 is afrontal view of an example light source comprising a linear array ofedge weighted light-emitting elements, while FIG. 11 illustrates anexample of a partial frontal view of two light sources comprising edgeweighted linear arrays of light-emitting elements arranged side by side.FIGS. 12 and 13 are a partial side perspective view and a frontalperspective view of the example light source of FIG. 10. FIG. 14 is aschematic of an example of a configuration for a light source and FIG.15 is an example flow chart for a method of using a light source.Examples of multi-groove and single-groove cylindrical Fresnel lensesare depicted in FIGS. 16A, 16B, 16C, and 16D. FIG. 17 illustrates anexample of a light source comprising a single-groove cylindrical Fresnellens. A double cylindrical Fresnel lens is shown in FIG. 18.

Turning now to FIG. 1, it illustrates an emission pattern 100 for anear-Lambertian light source such as an LED type light-emitting element.The emission pattern illustrates that the angular spread of lightoriginating from the near-Lambertian light source is broad and disperse,and the radiant intensity profile 110 is variable as the emission anglefrom the light source is varied from −90° to +90°. Accordingly, asurface illuminated by a near-Lambertian light source may not beuniformly irradiated with light.

FIG. 2 illustrates a simple schematic of an example of a regularlyspaced 36 mm linear array 200 of ten light-emitting elements 220.Regularly spaced implies that the spacing 240 between eachlight-emitting element may be the same. The light-emitting elements maybe mounted on a substrate 210, for example a printed circuit board(PCB).

FIG. 3 illustrates a plot 300 of an irradiance pattern at a fixed planelocated 6 mm away from the regularly spaced linear array of LEDs in FIG.2. The irradiance pattern of plot 300 may be generated using an opticalsimulation program such as Zemax. Curves 310, 320, 330, 340, 350, and360 approximate lines of constant irradiance at a surface 6 mm away fromthe light source oriented perpendicular to the 90° emission angle of1.80, 1.65, 1.30, 0.90, 0.40, and 0.20 W/cm² respectively. FIG. 3illustrates the angular spread of light emitted from the linearregular-spaced array in a widthwise axis and a lengthwise axis.Irradiance from the regularly spaced array varies across the twodimensional pattern decreasing in intensity from the center of thepattern towards the periphery.

FIG. 4 shows a plot 400 of the cross section of the irradiance patternof plot 300 taken along its major axis of symmetry, or along acenterline corresponding to the linear array. The irradiance profile 410illustrates that the irradiance may be somewhat uniform in a centralportion of the surface, but may decrease significantly towards theedges. For UV curing, a light source providing uniform irradiance at atarget surface may provide uniform curing rates across the targetsurface. To achieve uniform cure rates, a surface may be irradiatedusing a light source providing an emission pattern where the irradianceis above a minimum threshold and below a maximum threshold across thetarget surface. For example, when the irradiance is below a minimumthreshold, the cure rate may be slow and curing of the target surfacemay not be achieved. On the other hand, when the irradiance is above amaximum threshold, curing may proceed too rapidly causing overcuringwhich may damage the target surface. In general, when the differencebetween the maximum and minimum thresholds is smaller, more uniformcuring rates are achieved. For example, a metric to evaluate uniformitymay be defined using Equation (1):

Uniformity=(Maximum−Minimum)/Average(Maximum,Minimum)  (1),

wherein Maximum represents the maximum threshold and Minimum representsthe minimum threshold irradiance corresponding to providing uniformcuring rates. Equation (1) may then be solved for the minimum irradiancegiven a uniformity and maximum threshold irradiance:

Minimum=Maximum*(1−Uniformity/2)/(1+Uniformity/2)  (2)

For example, the case where the minimum threshold irradiance is equal tothe maximum threshold irradiance corresponds to perfectly uniformirradiance. As a further example, using Equation (2), for a uniformityof 20%, and a maximum irradiance of 1.83 W/cm², the minimum irradianceis calculated to be 1.497 W/cm². In this manner, a useable length of thelight output at a plane surface 6 mm from the evenly spaced linear arrayof LEDs of FIG. 2 may be determined from FIG. 4 to be 32.3 mm. Theuseable length corresponds to the length of the X-coordinate domain ofirradiance profile 410 that is within box 420, wherein box 420represents the X-coordinate values over which the emitted irradiance isbetween the minimum and maximum threshold values. Thus, over thiscalculated useable length, the irradiance uniformity may be 20% or lessaccording to Equation (2).

Turning now to FIG. 5, it illustrates an example of a 36 mm linear array500 of ten light-emitting elements (e.g., LEDs) with edge weightedspacing supported on a substrate 510, such as a PCB. The linear arraymay comprise a middle portion 516, which contains six LEDs 520 evenlydistributed therein with a first spacing 540, and two end portions eachcomprising two LEDs 530 distributed therein with a second spacing 536.Additionally, a third spacing 560 may be provided between the middleportion 516 and end portions 518. First spacing 524 betweenlight-emitting elements in the middle portion 516 may be larger thansecond spacing 536 between light-emitting elements in the end portions518, and third spacing 560 may be smaller than first spacing 524, butlarger than second spacing 536. As an example, the edge weighted lineararray 500 may be manufactured with the same physical dimensions, may besupplied with the same amount power, and may use the same number andtype of light-emitting elements (e.g. LEDs) as evenly spaced lineararray 200. In other words, the linear arrays of light-emitting elements500 and 200 may differ only in their spacing distribution of theirlight-emitting elements, linear array 200 employing even spacing betweenall ten light-emitting elements, and linear array 500 employing theabove-described edge weighted spacing.

The edge weighted spacing illustrated in FIG. 5 is an example of an edgeweighted linear array of light-emitting elements, and is not meant to belimiting. For example, edge weighted linear arrays of light-emittingelements may possess fewer or more than the ten LEDs illustrated inFIGS. 2 and 5. Furthermore, the middle portion of edge weighted lineararrays may comprise a larger or smaller number of LEDs and end portionsmay comprise a smaller or larger number of LEDs. Further still, thefirst spacing between light-emitting elements in the middle portion maybe larger or smaller than the first spacing 524, the second spacingbetween light-emitting elements in the end portions may be larger orsmaller than second spacing 536, and the third spacing between themiddle and end portions may be larger or smaller than third spacing 560.However, edge weighted spacing implies that the second spacing betweenlight-emitting elements in the end portions is smaller than the firstspacing between light-emitting elements in the middle portion.

FIG. 6 illustrates a plot 600 of an irradiance pattern at a fixed planelocated 6 mm away from the edge weighted linear array of LEDs in FIG. 5.The irradiance pattern of plot 600 may be generated using an opticalsimulation program such as Zemax. Curves 610, 620, 630, 640, 650, 660and 670 approximate lines of constant irradiance at a surface 6 mm awayfrom the light source oriented perpendicular to the 90° emission angleof 1.80, 1.65, 1.45, 1.30, 0.90, 0.40, and 0.20 W/cm² respectively.Irradiance from the edge weighted linear array varies across the twodimensional pattern, decreasing in intensity from the regionsencompassed by curves 620 at the center of the pattern outwards towardsthe periphery.

Turning now to FIG. 7, it shows a plot 700 of the cross section of theirradiance pattern of plot 600 taken along its major axis of symmetry,or along a centerline corresponding to the edge weighted linear array.The irradiance profile 710 illustrates that the irradiance may besomewhat more uniform in a central portion of the surface as compared tothe irradiance profile 410 of the evenly spaced linear array, but mayalso decrease significantly towards the edges of the profile. UsingEquation (2) as above, for a uniformity of 20%, and a maximum irradianceof 1.83 W/cm², the minimum irradiance is calculated to be 1.497 W/cm².In this manner, a useable length of the light output at a fixed planelocated 6 mm from the edge weighted linear array of LEDs of FIG. 5 maybe determined from FIG. 7 to be 37.8 mm. The useable length correspondsto the length of the X-coordinate domain of irradiance profile 710 thatis within box 720, wherein box 720 represents the X-coordinate valuesover which the emitted irradiance is between the minimum and maximumthreshold values.

Turning now to FIG. 8, it illustrates a plot 800 comparing theirradiance profiles 810 and 820 from FIGS. 4 and 7 of the evenly spacedand edge weighted linear arrays respectively. As shown in FIG. 8, edgeweighting the light-emitting elements, for example as in the lineararray of FIG. 5, may provide an increase in the useable length lightoutput of 5.5 mm relative to an evenly spaced linear array under theconditions of 20% uniformity corresponding to maximum and minimumthreshold irradiances of 1.83 W/cm² and 1.497 W/cm² respectively at afixed plane 6 mm from the light source. Box 830, corresponding to valuesof the irradiance between the minimum and maximum threshold irradiances,intersects irradiance profile 820 over a longer useable length ascompared to irradiance profile 810. Thus by redistributing thelight-emitting elements in an evenly spaced linear array to an edgeweighted linear array, the uniformity of the light source can beincreased while maintaining the dimensions (e.g., overall length) of thelinear array and the power supplied to the light source.

Further improvements to the irradiance profile can be made by usingLED's of different intensity. For example, higher intensity LEDs may beused in the middle portion (e.g., middle portion 516 in FIG. 5) of thelinear array, while lower intensity LEDs may be used in the endportions. Increasing or decreasing the intensity of light fromindividual light-emitting elements can be achieved by using LEDs fromdifferent bins, wherein LEDs from different bins emit light withdifferent intensities, using optical elements such as lenses to refract,reflect and/or diffract the light irradiated from individuallight-emitting elements. For example, optical elements may be coupled tothe light-emitting elements in the middle portion of the linear array tocollimate the light and increase the irradiance of light from thoseelements. As another example, a diffuser may be coupled to thelight-emitting elements in the end portions of the linear array to lowerthe irradiance of light irradiated from those elements. Furthermore,combinations of optical elements may be coupled to light-emittingelements in the middle and/or end portions to raise or lower theintensity of light irradiated from individual light-emitting elements.In the manners described above, edge weighting of linear arrays oflight-emitting elements may thus be achieved through lensing, applyingdifferential power, and by configuring the array with LEDs of differentintensity, in addition to the edge weighted spacing previously describedand illustrated in FIG. 5.

Turning now to FIG. 9, it illustrates a plot 900 comparing theirradiance profiles 810 and 820 from FIGS. 4 and 7 of the evenly spacedand edge weighted linear arrays respectively. In addition, theirradiance profile 940 of an edge weighted linear array of LEDs similarto array 500, except wherein the four centermost LED elements are lensedto provide a 20% boost in their irradiance, is plotted. As shown in FIG.9, coupling optical lens elements to the centermost LED elementsenhances the uniformity of the linear array of light-emitting elementsfurther, without supplying additional power or increasing the length ofthe linear array light source.

FIG. 10 illustrates a frontal view of a light source 1000 comprising anedge weighted linear array of twenty-seven light-emitting elements(e.g., LEDs) contained within a housing 1010. Light source 1000 mayfurther comprise a front cover 1016 at the front plane of the housing1010, a window 1020, and a plurality of fasteners 1030 for fixing thefront cover to housing 1010. Housing 1010 and front cover 1016 may bemanufactured from a rigid material such as metal, metal allow, plastic,or another material. The light-emitting elements may be mounted on asubstrate (not shown), such as a PCB, and the front surface of thesubstrate may have a reflective coating or surface such that lightirradiated from the light-emitting elements onto the substrate frontsurface is reflected towards the window.

Window 1020 may be transparent to light such as visible light and/or UVlight. Window 1020 may thus be constructed from glass, plastic, oranother transparent material. Window 1020 may be positionedapproximately centrally with respect to the widthwise dimension of thefront cover and a length of window 1020 may span the length of the frontplane and the front cover 1016 of the housing 1010. Furthermore, window1020 may be mounted so that its front face (1028 in FIG. 12) is flushwith the front cover of the housing 1010, and so that window sidewalls(1086 in FIG. 12) are flush with the housing sidewalls (1018 in FIG. 13)and front cover sidewalls (not shown). In other words, window sidewalls,housing sidewalls, and front cover sidewalls are aligned in the sameplane. Window 1020 may serve as a transparent cover for the edgeweighted linear array of light-emitting elements contained within thehousing, wherein light irradiated from the linear array is transmittedthrough window 1020 to a target surface, where for example, a curingreaction may be driven.

The linear array of light-emitting elements may be recessed under andapproximately centered below window 1020 with respect to the lengthwiseand widthwise dimensions of the window. Centering the linear array oflight-emitting elements below the window 1020 may help to preventirradiated light from being blocked by the lengthwise edges of thewindow where the window meets the front cover.

The edge weighted linear array comprises a middle portion 1052 betweentwo end portions 1062. Middle portion 1052 comprises twenty-one evenlyspaced light-emitting elements 1050 distributed with a first spacing1054, while end portions 1062 each comprise two light-emitting elements1060 with a second spacing 1064.

Furthermore, light source 1000 may comprise a third spacing 1068 betweenend portions 1062 and middle portion 1052, wherein the third spacing1068 is smaller than the first spacing 1054 and larger than the secondspacing 1064. Further still, light source 1000 may comprise a fourthspacing 1074 between the end portions 1062 and middle portions 1052.

The edge weighted spacing illustrated in FIG. 10 is an example of anedge weighted linear array of light-emitting elements, and is not meantto be limiting. For example, edge weighted linear arrays oflight-emitting elements may possess fewer or more than the twenty-sevenLEDs illustrated in FIG. 10. Furthermore, the middle portion of edgeweighted linear arrays may comprise a larger or smaller number of LEDsand end portions may comprise a smaller or larger number of LEDs.Further still, the first spacing between light-emitting elements in themiddle portion may be larger or smaller than the first spacing 1054, thesecond spacing between light-emitting elements in the end portions maybe larger or smaller than second spacing 1064, and the third spacingbetween the middle and end portions may be larger or smaller than thirdspacing 1068. However, edge weighted spacing implies that the secondspacing between light-emitting elements in the end portions is smallerthan the first spacing between light-emitting elements in the middleportion.

The first and last light-emitting elements in the edge weighted lineararray may be positioned directly adjacent to the window sidewalls 1086of the window 1020. In this manner, the edge weighted linear array oflight-emitting elements may span the length of window 1020 and frontcover 1016 of housing 1010. As illustrated in FIG. 10, the windowsidewalls 1086 may have a thickness wherein the distance from the firstor last light-emitting element of the linear array to the externalsurface of the corresponding window sidewall may be one half or less thefirst spacing between middle portion light-emitting elements. In someexamples a gap 1082 between the window sidewalls and the first and lastlight-emitting elements in the linear array may exist. Gap 1082 mayallow for tolerance stackup and assembly of the light sources.

The light source 1000 may further comprise coupling optics or lensingelements (not shown) positioned between the linear array oflight-emitting elements and the window. Coupling optics may serve to atleast reflect, refract, collimate and/or diffract irradiated light fromthe linear array. Coupling optics may also be integrated with window1020. For example, a diffuser or diffracting layer may be etched orlaminated onto the back surface of window 1020 that faces the lineararray. Further still, coupling optics may also be integrated into thefront surface of window 1020 that faces the target surface. In someexamples, coupling optics may further comprise a cylindrical lens, forexample a cylindrical Fresnel lens (see FIG. 17), wherein the lineararray of light-emitting elements may be aligned with and emit lightthrough the cylindrical lens. In this manner, the cylindrical lens mayreduce the angular spread of light in a widthwise axis of the lineararray, thereby enhancing the uniformity of emitted light across awidthwise axis. In some examples the cylindrical lens may be acylindrical Fresnel lens. Accordingly, the uniformity of emitted lightin a widthwise axis (e.g., axis 580 in FIG. 5, and axis 680 in FIG. 6)may be enhanced as compared to the uniformity of emitted light inwidthwise axis as compared to the irradiance patterns illustrated inFIGS. 4 and 6 for linear arrays of light-emitting elements emittinglight through a window. Further still, coupling optics may furthercomprise a double cylindrical Fresnel lens (see FIG. 18) wherein twocylindrical Fresnel lenses are overlaid on top of one another such thatenhanced collimating and focusing power for reducing the angular spreadof light in a widthwise axis is achieved to a greater extent as comparedwith coupling optics comprising a single cylindrical Fresnel lens.

Turning now to FIG. 11, it illustrates a partial frontal view of twolight sources 1110, 1120 arranged side by side. Light sources 1110 and1120 may each be identical to light source 1000. Thus, light sources1110, 1120 may each comprise an edge weighted linear array oflight-emitting elements. Each linear array comprises light-emittingelements 1050 distributed with a first spacing 1054 in a middle portion,and light-emitting elements 1060 distributed with a second spacing 1064in end portions. Furthermore, light sources 1110 and 1120 comprise athird spacing 1068 and a fourth spacing 1074 between light-emittingelements 1050, 1060 of the middle and end portions respectively. Thirdspacing 1068 may be larger than second spacing 1064 and smaller thanfirst spacing 1054. As described above, edge weighting the linear arrayof light-emitting elements increases the useable length of light outputfrom each light source.

Furthermore, first and last light-emitting elements in the end portionsof light sources 1120 and 1110 respectively are positioned adjacent towindow sidewalls 1086, wherein the window sidewalls 1086 span the lengthof the front plane of each light source housing. Positioning the firstand last light-emitting elements in the linear arrays adjacent to windowsidewalls 1086 may allow light sources 1120 and 1110 to irradiate lightacross the entire length of the window. Positioning the first and lastlight-emitting elements in the linear arrays adjacent to windowsidewalls 1086 may comprise positioning the first and lastlight-emitting elements wherein there may be a small gap 1082 betweenthe window sidewalls and the first and last light-emitting elementsrespectively.

Further still, the window sidewalls 1086 are flush with the sidewalls ofthe housings of light sources 1120 and 1110, the window and housingsidewalls extending backward perpendicularly from the front plane of thehousing. Aligning the window sidewalls to be flush with the housingsidewalls may reduce spacing between and may maintain continuity ofirradiated light across multiple light sources arranged side by side.

In this manner, the total distance from the last light-emitting elementof a linear array of light source 1120 to the first light-emittingelement of light source 1110 when positioned side by side may be thesame or less than the first spacing between middle portionlight-emitting elements. Accordingly, for a single light source, thedistance from the last light-emitting element of the linear array to theexternal surface of the corresponding window sidewall may be one half orless the first spacing between middle portion light-emitting elements.Thus, light irradiated from light sources 1120 and 1110 arranged side byside may be more uniform as compared to light irradiated fromconventional light sources arranged side by side.

FIG. 12 illustrates a partial side perspective view of the light source1000 of FIG. 10, comprising front cover 1016, window 1020, fasteners1030 and linear array of light-emitting elements 1090. Window 1020comprises front face 1028 and window sidewalls 1086. Both window frontface 1028 and window sidewalls 1086 are transparent. Accordingly, aportion of light irradiated from end portion light-emitting elementsadjacent to and near window sidewalls 1086 may be irradiated throughwindow sidewalls 1086. Irradiation of light through window sidewalls1086 of light sources may thereby reduce non-uniformities in irradiatedlight across multiple light sources arranged adjacently side by side ascompared to conventional light sources arranged side by side. Windowsidewalls 1086 are flush with the sides of front cover 1016 and housingsidewalls 1018 so that light sources can be placed side by side in aflush arrangement wherein a gap between the side by side light sourcesis reduced. To this end, fasteners 1030 mounted in housing sidewalls1018 may also be recessed from the plane of housing sidewalls 1018 whenfully secured. As previously described, aligning the window sidewalls tobe flush with the housing sidewalls may reduce spacing between and maymaintain continuity of irradiated light across multiple light sourcesarranged side by side.

Turning now to FIG. 13, it illustrates a perspective view of the examplelight source 1000 of FIG. 10. The light source comprises a housing 1010containing a linear array of light-emitting elements, a window and afront cover 1016 at the front plane of the housing 1010, sidewalls 1018,and fasteners 1030. As illustrated, the light source 1000 may have ahousing 1010 shaped as a square or rounded rectangular box. Otherhousing shapes where sidewalls extend backwards perpendicularly from thefront plane of the housing and where light sources may be positionedflush when side by side may be used.

Turning now to FIGS. 16A and 16B, they illustrate perspective andcross-section views, respectively, of an example of a multiple-groovecylindrical Fresnel lens 1600. The multiple-groove cylindrical Fresnellens in FIGS. 16A and 16B have sixteen grooves 1620, however in otherexamples, a multiple-groove cylindrical Fresnel lens may have fewer ormore grooves. As an example, a multiple-groove cylindrical Fresnel lensmay comprise 50 grooves. As a further example, a cylindrical Fresnellens may comprise a single-groove cylindrical Fresnel lens 1602 having asingle groove 1650 (e.g., a single prism), as illustrated by theperspective and cross-section views of FIGS. 16C and 16D, respectively.In general, as the number of grooves in a cylindrical Fresnel lens isincreased, the thickness of the lens may decrease. In some examples,linear cylindrical Fresnel lenses may be manufactured from glass by aglass molding process, or optically transparent plastic. Glass lensesmay be dimensionally more heat stable at higher heat loads or highertemperatures, such as temperatures above 120° C., as compared toplastic. However, glass cylindrical Fresnel lenses comprising a largenumber of grooves may be more difficult to manufacture precisely, ascompared to plastic cylindrical Fresnel lenses because it may bedifficult to achieve the fine sharp edges and points precisely by glassmolding. For example, glass molded lenses may tend to have rounded edgesand it may be more difficult to achieve multiple grooves of a fine pitchfor lenses with large numbers of grooves. Manufacturing Fresnel lensesusing plastic may allow achieving sharper prism ridges and finer prismpitch surfaces for Fresnel lenses with multiple grooves.

In order to collimate and reduce angular spread of emitted light in awidthwise axis 1604, the one or more cylindrical Fresnel grooves may beoriented parallel to the lengthwise axis 1608 of the light source.Furthermore, the cylindrical Fresnel lens may be oriented in a groove-inorientation, wherein the cylindrical Fresnel lens grooved surface 1630faces toward the light source and the planar lens surface 1640 facesaway from the light source, or a groove-out orientation, wherein thecylindrical Fresnel lens grooved surface 1630 faces away from the lightsource and the planar lens surface 1640 faces towards from the lightsource. The groove-in and groove-out orientation of the cylindricalFresnel lens may impact the transmission efficiency of light through thecylindrical Fresnel lens. The geometry and shapes of the grooves of thecylindrical Fresnel lenses shown in FIGS. 16A, 16B, 16C, and 16D are forillustrative purposes and may not be drawn to scale. The cylindricalFresnel lens may further comprise transparent lengthwise edges 1610. Asan example, the cylindrical Fresnel lens may mount to the light sourceat the lengthwise edges 1610.

Turning now to FIG. 18, it illustrates a cross-section of an example ofa double cylindrical Fresnel lens 1800, wherein two cylindrical Fresnellenses 1820 and 1840 are overlaid on top of one another. In FIG. 18,each of the two cylindrical Fresnel lenses 1820 and 1840 are identical,with the same number and shapes of grooves, however, in other exampledouble cylindrical Fresnel lenses the number and shapes of grooves ofeach of the lenses 1820 and 1840 may be different. Furthermore, in FIG.18, each of the two cylindrical Fresnel lenses are oriented with agroove-in orientation, wherein incident light 1850 enters the groovedsurfaces 1842 and 1822 and exits the planar surfaces 1844 and 1824 ofcylindrical Fresnel lenses 1840 and 1820, respectively. In other exampledouble cylindrical Fresnel lens configurations, the orientation of oneor both Fresnel lenses may be oriented with a groove-out orientationwith respect to the incident light 1850. In this manner, a doublecylindrical Fresnel lens may achieve enhanced collimating and focusingpower from a double cylindrical Fresnel lens configuration, and mayreduce and collimate the angular spread of light in a widthwise axis toa greater extent as compared to a single cylindrical Fresnel lens. As afurther example, more than two cylindrical Fresnel lenses may be stackedor overlaid to achieve enhanced collimating and focusing power forreducing and collimating the angular spread of light in a widthwise axisto a greater extent as compared to a single cylindrical Fresnel lens.

Turning now to FIG. 17, it illustrates a partial side perspective viewof another example light source 1700. Light source 1700 may be similarto above-described light sources 1000, 1110 and 1120, and may furthercomprise coupling optics. For example, coupling optics of light source1700 may comprise a cylindrical lens, for example cylindrical Fresnellens 1720. Similar to light sources 1000, 1110, and 1120, FIG. 17 alsoshows light source 1700 including front cover 1016, fasteners 1030,housing sidewalls 1018, and the linear array of light-emitting elements1090. Cylindrical Fresnel lens 1720 may comprise a single-groove ormultiple-groove cylindrical Fresnel lens (e.g., cylindrical Fresnellenses 16C and 16A respectively), wherein cylindrical Fresnel lens 1720may comprise one or more grooves 1722 on a grooved surface 1724.Cylindrical Fresnel lens 1720 may have a groove-in orientation whereingrooved surface 1724 may face towards the light-emitting elements 1090and planar surface 1728 may face away from the light-emitting elements1090 as shown in FIG. 17. Alternately, cylindrical Fresnel lens 1720 mayhave a groove-out orientation, wherein grooved surface 1724 may faceaway from the light-emitting elements 1090 and planar surface 1728 ofcylindrical Fresnel lens may face towards the light-emitting elements1090. Cylindrical Fresnel lens 1720 may also comprise a doublecylindrical Fresnel lens. Both planar surface 1728 and sidewalls 1786 ofcylindrical Fresnel lens are transparent. Accordingly, a portion oflight irradiated from end portion light-emitting elements adjacent toand near lens sidewalls 1786 may be irradiated through lens sidewalls1786. Irradiation of light through lens sidewalls 1786 of light sourcesmay thereby reduce non-uniformities in irradiated light across multiplelight sources arranged adjacently side by side as compared toconventional light sources arranged side by side. Lens sidewalls 1786may be flush with the sides of front cover 1016 and housing sidewalls1018 so that light sources can be placed side by side in a flusharrangement wherein a gap between the side by side light sources isreduced. To this end, fasteners 1030 mounted in housing sidewalls 1018may also be recessed from the plane of housing sidewalls 1018 when fullysecured. As previously described, aligning the lens sidewalls 1786 to beflush with the housing sidewalls may reduce spacing between and maymaintain continuity of irradiated light across multiple light sourcesarranged side by side. Furthermore, lens sidewalls 1786 may extendperpendicularly back from the front plane. In this manner, multiplelight sources may be aligned flushly side by side wherein first and lastlight-emitting elements in the end portions of side by side lightsources (e.g., similar to the arrangement of light sources 1120 and 1110respectively in FIG. 11) are positioned adjacent to lens sidewalls 1786,wherein the lens sidewalls 1786 span the length of the front plane ofeach light source housing. Positioning the first and last light-emittingelements in the linear arrays adjacent to lens sidewalls 1786 may allowside by side light sources to irradiate light across the entire lengthof the lens. Positioning the first and last light-emitting elements inthe linear arrays adjacent to lens sidewalls 1786 may comprisepositioning the first and last light-emitting elements wherein there maybe a small gap (e.g., gap 1082) between the window sidewalls and thefirst and last light-emitting elements respectively.

As another example, light source 1700 may further comprise a transparentwindow (not shown) mounted in a front plane of the housing and coveringthe front face of the cylindrical Fresnel lens 1720, wherein a frontface of the window is aligned approximately flush with the front planeof the housing, and window sidewalls are aligned flushly with thehousing sidewalls 1018. Aligning the lens sidewalls 1786 and windowsidewalls to be flush with the housing sidewalls may reduce spacingbetween and may maintain continuity of irradiated light across multiplelight sources arranged side by side.

Furthermore, the linear array of light-emitting elements 1090 maycomprise an edge weighted linear array of light-emitting elements, asdescribed above for light sources 1000, 1110, and 1120. Examples of edgeweighted linear arrays of light-emitting elements and light irradiancepatterns emitted therefrom are illustrated in FIGS. 5-9. Accordingly,the linear array may comprise light-emitting elements distributed with afirst spacing in a middle portion, and light-emitting elementsdistributed with a second spacing in end portions. Furthermore, thelinear array may comprise a third spacing and a fourth spacing betweenlight-emitting elements, of the middle and end portions respectively.The third spacing may be larger than second spacing and smaller thanfirst spacing. As described above, edge weighting the linear array oflight-emitting elements may enhance the uniformity of emitted light in alengthwise direction, and thereby may increase the useable length oflight output from each light source while maintaining the dimensions(e.g., overall length) of the linear array and power supplied to thelight source as compared to an evenly spaced linear array. Furthermore,the cylindrical Fresnel lens 1720 may enhance uniformity of emittedlight in a widthwise axis, and thereby may increase the usable length oflight output from each light source while maintaining the dimensions(e.g., overall width) of the linear array and power supplied to thelight source as compared to a conventional light source that may notcomprise emitting light through a cylindrical Fresnel lens.

In this manner, the total distance from the last light-emitting elementof a linear array light source 1700 to the first light-emitting elementof another light source 1700 positioned side by side may be the same orless than the first spacing between middle portion light-emittingelements. Accordingly, for a single light source, the distance from thelast light-emitting element of the linear array to the external surfaceof the corresponding window sidewall may be one half or less the firstspacing between middle portion light-emitting elements. Thus, lightirradiated from multiple light sources 1700 arranged side by side may bemore uniform as compared to light irradiated from conventional lightsources with evenly spaced linear arrays of light-emitting elementsarranged side by side.

In this manner, a light source may comprise a cylindrical Fresnel lens,a linear array of light-emitting elements, the linear array aligned withand emitting light through the cylindrical Fresnel lens, wherein thecylindrical Fresnel lens reduces the angular spread of light in awidthwise axis of the linear array. The light source may furthercomprise a housing, wherein a window may be mounted in a front plane ofthe housing, a window length spanning the length of the front plane, anda linear array of light-emitting elements within the housing.Furthermore, the linear array may span the window length, wherein firstand last light-emitting elements of the linear array are positionedadjacent to widthwise edges of the window, and wherein window sidewallsat the widthwise edges are aligned flush with housing sidewalls. Thewindow may comprise a front face and the window sidewalls, the frontface flush with the front plane, and the window sidewalls extendingperpendicularly back from the front plane.

The linear array of light-emitting elements may further comprise amiddle portion in between two end portions, the linear array having onlya single row of elements. The middle portion may comprise a plurality oflight-emitting elements distributed over the middle portion with a firstspacing throughout the middle portion, and each of the end portions maycomprise a plurality of light-emitting elements distributed over the endportion with a second spacing throughout each end portion. The firstspacing may be greater than the second spacing.

The linear array of light-emitting elements may further comprise a thirdspacing between the middle portion and each of the end portions, whereinthe third spacing may be greater than the second spacing and less thanthe first spacing. The plurality of light-emitting elements in themiddle portion may have a first irradiance, and the plurality oflight-emitting elements in each end portion may have a secondirradiance. Each of the plurality of light-emitting elements in themiddle portion may comprise a higher intensity light-emitting elementthan each of the plurality of light-emitting elements in the endportions, and the first irradiance may be greater than the secondirradiance.

Further still, the plurality of light-emitting elements in the middleportion may each comprises an optical element, each optical elementincreasing a first irradiance of its corresponding light-emittingelement, wherein the first irradiance is greater than the secondirradiance. Further still, the plurality of light-emitting elements inthe end portions may each comprise an optical element, wherein theoptical element decreases a second irradiance of its correspondinglight-emitting element, and wherein the first irradiance is greater thanthe second irradiance.

Further still, the plurality of light-emitting elements in the middleportion may be supplied with a first drive current, the plurality oflight-emitting elements in the end portions may be supplied with asecond drive current, wherein the first drive current may be greaterthan the second drive current.

Referring now to FIG. 14, it illustrates a block diagram for an exampleconfiguration of lighting system 1400. In one example, lighting system1400 may comprise a light-emitting subsystem 1412, a controller 1414, apower source 1416 and a cooling subsystem 1418. The light-emittingsubsystem 1412 may comprise a plurality of semiconductor devices 1419.The plurality of semiconductor devices 1419 may be a linear array 1420of light-emitting elements such as a linear array of LED devices, forexample. Semiconductor devices may provide radiant output 1424. Theradiant output 1424 may be directed to a workpiece 1426 located at afixed plane from lighting system 1400. Furthermore, the linear array oflight-emitting elements may be an edge weighted linear array oflight-emitting elements, wherein one or more methods are employed toincrease the useable length of light output at workpiece 1426. Forexample, one or more of edge weighted spacing, lensing (e.g. providingcoupling optics) of individual light-emitting elements, providingindividual light-emitting elements of different intensity, and supplyingdifferential current to individual LEDs may be employed as describedabove.

The radiant output 1424 may be directed to the workpiece 1426 viacoupling optics 1430. The coupling optics 1430, if used, may bevariously implemented. As an example, the coupling optics may includeone or more layers, materials or other structures interposed between thesemiconductor devices 1419 and window 1464, and providing radiant output1424 to surfaces of the workpiece 1426. As an example, the couplingoptics 1430 may include a micro-lens array to enhance collection,condensing, collimation or otherwise the quality or effective quantityof the radiant output 1424. As another example, the coupling optics 1430may include a micro-reflector array. In employing such a micro-reflectorarray, each semiconductor device providing radiant output 1424 may bedisposed in a respective micro-reflector, on a one-to-one basis. Asanother example, a linear array of semiconductor devices 1420 providingradiant output 24 and 25 may be disposed in macro-reflectors, on amany-to-one basis. In this manner, coupling optics 1430 may include bothmicro-reflector arrays, wherein each semiconductor device is disposed ona one-to-one basis in a respective micro-reflector, and macro-reflectorswherein the quantity and/or quality of the radiant output 1424 from thesemiconductor devices is further enhanced by macro-reflectors.

Each of the layers, materials or other structure of coupling optics 1430may have a selected index of refraction. By properly selecting eachindex of refraction, reflection at interfaces between layers, materialsand other structures in the path of the radiant output 1424 may beselectively controlled. As an example, by controlling differences insuch indexes of refraction at a selected interface, for example window1464, disposed between the semiconductor devices to the workpiece 1426,reflection at that interface may be reduced or increased so as toenhance the transmission of radiant output at that interface forultimate delivery to the workpiece 1426. For example, the couplingoptics may include a dichroic reflector where certain wavelengths ofincident light are absorbed, while others are reflected and focused tothe surface of workpiece 1426.

The coupling optics 1430 may be employed for various purposes. Examplepurposes include, among others, to protect the semiconductor devices1419, to retain cooling fluid associated with the cooling subsystem1418, to collect, condense and/or collimate the radiant output 1424, orfor other purposes, alone or in combination. As a further example, thelighting system 1400 may employ coupling optics 1430 so as to enhancethe effective quality, uniformity, or quantity of the radiant output1424, particularly as delivered to the workpiece 1426.

As a further example, coupling optics 1430 may comprise a cylindricalFresnel lens such as a linear cylindrical Fresnel lens for collimatingand/or focusing the light emitted from the linear array 1420 ofsemiconductor devices 1419. In particular, a cylindrical Fresnel lensmay be aligned with the linear array 1420, wherein emitted lighttherefrom is emitted through the cylindrical Fresnel lens and whereinthe cylindrical Fresnel lens reduces the angular spread of light in awidthwise axis of the linear array, the linear array spanning a lenslength. In some examples, a cylindrical Fresnel lens may be used inplace of a window, such as window 1020, as shown in FIG. 17. Thecylindrical Fresnel lens may be a single-groove lens or a multiplegroove lens, and may also comprise a double cylindrical Fresnel lens(see FIG. 18) to further reduce the angular spread of emitted light in awidthwise axis as compared to a single cylindrical Fresnel lens.

Selected of the plurality of semiconductor devices 1419 may be coupledto the controller 1414 via coupling electronics 1422, so as to providedata to the controller 1414. As described further below, the controller1414 may also be implemented to control such data-providingsemiconductor devices, e.g., via the coupling electronics 1422. Thecontroller 1414 may be connected to, and may be implemented to control,the power source 1416, and the cooling subsystem 1418. For example, thecontroller may supply a larger drive current to light-emitting elementsdistributed in the middle portion of linear array 1420 and a smallerdrive current to light-emitting elements distributed in the end portionsof linear array 1420 in order to increase the useable length of lightirradiated at workpiece 1426. Moreover, the controller 1414 may receivedata from power source 1416 and cooling subsystem 1418. In one example,the irradiance at one or more locations at the workpiece 1426 surfacemay be detected by sensors and transmitted to controller 1414 in afeedback control scheme. In a further example, controller 1414 maycommunicate with a controller of another lighting system (not shown inFIG. 14) to coordinate control of both lighting systems. For example,controllers 1414 of multiple lighting systems may operate in amaster-slave cascading control algorithm, where the setpoint of one ofthe controllers is set by the output of the other controller. Othercontrol strategies for operation of lighting system 10 in conjunctionwith another lighting system may also be used. As another example,controllers 1414 for multiple lighting systems arranged side by side maycontrol lighting systems in an identical manner for increasinguniformity of irradiated light across multiple lighting systems.

In addition to the power source 1416, cooling subsystem 1418, andlight-emitting subsystem 1412, the controller 1414 may also be connectedto, and implemented to control internal element 1432, and externalelement 1434. Element 1432, as shown, may be internal to the lightingsystem 1410, while element 1434, as shown, may be external to thelighting system 1410, but may be associated with the workpiece 1426(e.g., handling, cooling or other external equipment) or may beotherwise related to a photoreaction (e.g. curing) that lighting system1410 supports.

The data received by the controller 1414 from one or more of the powersource 1416, the cooling subsystem 1418, the light-emitting subsystem1412, and/or elements 1432 and 1434, may be of various types. As anexample the data may be representative of one or more characteristicsassociated with coupled semiconductor devices 1419. As another example,the data may be representative of one or more characteristics associatedwith the respective light-emitting subsystem 1412, power source 1416,cooling subsystem 1418, internal element 1432, and external element 1434providing the data. As still another example, the data may berepresentative of one or more characteristics associated with theworkpiece 1426 (e.g., representative of the radiant output energy orspectral component(s) directed to the workpiece). Moreover, the data maybe representative of some combination of these characteristics.

The controller 1414, in receipt of any such data, may be implemented torespond to that data. For example, responsive to such data from any suchcomponent, the controller 1414 may be implemented to control one or moreof the power source 1416, cooling subsystem 1418, light-emittingsubsystem 1412 (including one or more such coupled semiconductordevices), and/or the elements 32 and 34. As an example, responsive todata from the light-emitting subsystem indicating that the light energyis insufficient at one or more points associated with the workpiece, thecontroller 1414 may be implemented to either (a) increase the powersource's supply of power to one or more of the semiconductor devices,(b) increase cooling of the light-emitting subsystem via the coolingsubsystem 1418 (e.g., certain light-emitting devices, if cooled, providegreater radiant output), (c) increase the time during which the power issupplied to such devices, or (d) a combination of the above.

Individual semiconductor devices 1419 (e.g., LED devices) of thelight-emitting subsystem 1412 may be controlled independently bycontroller 1414. For example, controller 1414 may control a first groupof one or more individual LED devices to emit light of a firstintensity, wavelength, and the like, while controlling a second group ofone or more individual LED devices to emit light of a differentintensity, wavelength, and the like. The first group of one or moreindividual LED devices may be within the same linear array 1420 ofsemiconductor devices, or may be from more than one linear array ofsemiconductor devices 1420 from multiple lighting systems 1400. Lineararray 1420 of semiconductor device may also be controlled independentlyby controller 1414 from other linear arrays of semiconductor devices inother lighting systems. For example, the semiconductor devices of afirst linear array may be controlled to emit light of a first intensity,wavelength, and the like, while those of a second linear array inanother lighting system may be controlled to emit light of a secondintensity, wavelength, and the like.

As a further example, under a first set of conditions (e.g. for aspecific workpiece, photoreaction, and/or set of operating conditions)controller 1414 may operate lighting system 1410 to implement a firstcontrol strategy, whereas under a second set of conditions (e.g. for aspecific workpiece, photoreaction, and/or set of operating conditions)controller 1414 may operate lighting system 1410 to implement a secondcontrol strategy. As described above, the first control strategy mayinclude operating a first group of one or more individual semiconductordevices (e.g., LED devices) to emit light of a first intensity,wavelength, and the like, while the second control strategy may includeoperating a second group of one or more individual LED devices to emitlight of a second intensity, wavelength, and the like. The first groupof LED devices may be the same group of LED devices as the second group,and may span one or more arrays of LED devices, or may be a differentgroup of LED devices from the second group, but the different group ofLED devices may include a subset of one or more LED devices from thesecond group.

The cooling subsystem 1418 may be implemented to manage the thermalbehavior of the light-emitting subsystem 1412. For example, the coolingsubsystem 1418 may provide for cooling of light-emitting subsystem 1412,and more specifically, the semiconductor devices 1419. The coolingsubsystem 1418 may also be implemented to cool the workpiece 1426 and/orthe space between the workpiece 1426 and the lighting system 1410 (e.g.,the light-emitting subsystem 1412). For example, cooling subsystem 1418may comprise an air or other fluid (e.g., water) cooling system. Coolingsubsystem 1418 may also include cooling elements such as cooling finsattached to the semiconductor devices 1419, or linear array 1420thereof, or to the coupling optics 1430. For example, cooling subsystemmay include blowing cooling air over the coupling optics 1430, whereinthe coupling optics 1430 are equipped with external fins to enhance heattransfer.

The lighting system 1410 may be used for various applications. Examplesinclude, without limitation, curing applications ranging from inkprinting to the fabrication of DVDs and lithography. The applications inwhich the lighting system 1410 may be employed can have associatedoperating parameters. That is, an application may have associatedoperating parameters as follows: provision of one or more levels ofradiant power, at one or more wavelengths, applied over one or moreperiods of time. In order to properly accomplish the photoreactionassociated with the application, optical power may be delivered at ornear the workpiece 1426 at or above one or more predetermined levels ofone or a plurality of these parameters (and/or for a certain time, timesor range of times).

In order to follow an intended application's parameters, thesemiconductor devices 1419 providing radiant output 1424 may be operatedin accordance with various characteristics associated with theapplication's parameters, e.g., temperature, spectral distribution andradiant power. At the same time, the semiconductor devices 1419 may havecertain operating specifications, which may be associated with thesemiconductor devices' fabrication and, among other things, may befollowed in order to preclude destruction and/or forestall degradationof the devices. Other components of the lighting system 1410 may alsohave associated operating specifications. These specifications mayinclude ranges (e.g., maximum and minimum) for operating temperaturesand applied electrical power, among other parameter specifications.

Accordingly, the lighting system 1410 may support monitoring of theapplication's parameters. In addition, the lighting system 1410 mayprovide for monitoring of semiconductor devices 1419, including theirrespective characteristics and specifications. Moreover, the lightingsystem 1410 may also provide for monitoring of selected other componentsof the lighting system 1410, including its characteristics andspecifications.

Providing such monitoring may enable verification of the system's properoperation so that operation of lighting system 1410 may be reliablyevaluated. For example, lighting system 1410 may be operating improperlywith respect to one or more of the application's parameters (e.g.temperature, spectral distribution, radiant power, and the like), anycomponent's characteristics associated with such parameters and/or anycomponent's respective operating specifications. The provision ofmonitoring may be responsive and carried out in accordance with the datareceived by the controller 1414 from one or more of the system'scomponents.

Monitoring may also support control of the system's operation. Forexample, a control strategy may be implemented via the controller 1414,the controller 1414 receiving and being responsive to data from one ormore system components. This control strategy, as described above, maybe implemented directly (e.g., by controlling a component throughcontrol signals directed to the component, based on data respecting thatcomponents operation) or indirectly (e.g., by controlling a component'soperation through control signals directed to adjust operation of othercomponents). As an example, a semiconductor device's radiant output maybe adjusted indirectly through control signals directed to the powersource 1416 that adjust power applied to the light-emitting subsystem1412 and/or through control signals directed to the cooling subsystem1418 that adjust cooling applied to the light-emitting subsystem 1412.

Control strategies may be employed to enable and/or enhance the system'sproper operation and/or performance of the application. In a morespecific example, control may also be employed to enable and/or enhancebalance between the linear array's radiant output and its operatingtemperature, so as, e.g., to preclude heating the semiconductor devices1419 beyond their specifications while also directing sufficient radiantenergy to the workpiece 1426, for example, to carry out a photoreactionof the application.

In some applications, high radiant power may be delivered to theworkpiece 1426. Accordingly, the light-emitting subsystem 1412 may beimplemented using a linear array of light-emitting semiconductor devices1420. For example, the light-emitting subsystem 1412 may be implementedusing a high-density, light-emitting diode (LED) array. Although LEDarrays may be used and are described in detail herein, it is understoodthat the semiconductor devices 1419, and linear arrays 1420 thereof, maybe implemented using other light-emitting technologies without departingfrom the principles of the invention; examples of other light-emittingtechnologies include, without limitation, organic LEDs, laser diodes,other semiconductor lasers.

In this manner, a lighting system may comprise a power supply, a coolingsubsystem, and a light-emitting subsystem. The light-emitting subsystemmay comprise a housing, a window mounted in a front plane of thehousing, a window length spanning a front plane length, and a lineararray of light-emitting elements contained within the housing. Thelight-emitting subsystem may further comprise coupling optics, whereinthe coupling optics comprise a cylindrical Fresnel lens mounted in afront plane of the housing. The linear array may be aligned with andemit light through the cylindrical Fresnel lens, wherein the cylindricalFresnel lens reduces the angular spread of light in the widthwise axisof the linear array, the linear array spanning a lens length.Furthermore, the linear array may span the window length, wherein firstand last light-emitting elements of the linear array may be positionedadjacent to widthwise edges of the window. Window sidewalls at thewidthwise edges may be aligned flush with housing sidewalls, the windowsidewalls extending perpendicularly back from the front plane.

Further still, the linear array of light-emitting elements may comprisea middle portion in between two end portions, the linear array havingonly a single row of elements. The middle portion may comprise aplurality of light-emitting elements distributed over the middle portionwith a first spacing throughout the middle portion; and each of the endportions may comprise a plurality of light-emitting elements distributedover the end portion with a second spacing throughout each end portion,the first spacing greater than the second spacing.

The lighting system may further comprise a controller, includinginstructions executable to irradiate light from the light-emittingelements distributed over the middle portion having a first irradiance,and to irradiate light from light-emitting elements distributed over theend portions having a second irradiance, wherein the first irradiance isgreater than the second irradiance. Furthermore, the coupling optics mayfurther comprise first optical elements at each of the plurality oflight-emitting elements in the middle portion and second opticalelements at each of the plurality of light-emitting elements in the endportions. The cooling subsystem may comprise a heat sink with coolingfins conductively attached to a back surface of the linear array oflight-emitting elements, and a cooling fan.

Turning now to FIG. 15, it illustrates a flow chart for an examplemethod 1500 of irradiating a target surface. Method 1500 begins at 1510where the dimensions of the target surface to be irradiated aredetermined. The target surface may comprise a portion of a surface or anentire surface. The target surface may further comprise a portion of asurface or object to be uniformly irradiated. For example, a firstportion of the target surface may be cured with enhanced irradianceuniformity (e.g., uniformity determined using Equations (1) and (2)) anda second portion of the target surface may be cured with a non-enhancedirradiance uniformity. As an example, the first portion may be a centralportion, and the second portion may be a periphery portion. In otherexamples the first and second portions may be a left and right sideportion, and other apportioning schemes may be used as appropriate tothe target surface to be irradiated.

Continuing at 1520, the number of edge weighted linear array lightsources is determined. For example, one or a plurality of edge weightedlinear array light sources arranged side by side may be used toirradiate the target surface. The number of light sources may bedetermined based one or more factors including the dimensions of thetarget surface to be irradiated, the irradiance pattern of the one orplurality of light sources, the dimension of the light sources, thepower supplied to the light sources, and the target surface exposuretime, among other factors. For example if the length of the targetsurface is very long, multiple light sources arranged side by side maybe used to irradiate the entire length of the target surface.Furthermore, each of the one or plurality of light sources may comprisecoupling optics, wherein the coupling optics include a linear array oflight-emitting elements aligned with and emitting light through acylindrical Fresnel lens. Further still, the coupling optics maycomprise a double cylindrical Fresnel lens.

Next, method 1500 continues at 1530 where irradiance uniformitycalculations may be performed. The uniformity calculations may becalculated using Equation (1) and (2) as well as knowledge of theirradiance patterns and irradiance profiles of the light sources. Forexample, irradiance patterns and irradiance profiles may bepredetermined based on sensor measurements and/or optical simulations.Furthermore, using Equation (2), a maximum irradiance, and apredetermined uniformity level, a minimum irradiance intensity may becalculated for irradiance of a target surface at a fixed plane locatedat specific distance from the one or more light sources. Further still,performing uniformity calculations may include toggling one or more ofthe power supplied to the light source, the maximum irradiance emittedfrom the light source, the distance of the target surface from the lightsource, the irradiance exposure time, and other factors. For example,positioning the target surface at a fixed plane closer to one or morelight sources may increase the area of the target surface meeting aspecific irradiance uniformity, however, maximum irradiance levels atthe closer fixed plane may exceed a maximum irradiance threshold.Consequently, the power supplied to the one or more light sources may bereduced to lower the maximum irradiance threshold while maintaining thesame irradiance uniformity.

Method 1500 continues at 1540 where it is determined if irradianceuniformity is to be enhanced. For example, based on 1520 and 1530, itmay be determined that irradiance uniformity is to be enhanced in orderto irradiate a target surface with a predetermined irradiance uniformitywithin a predetermined irradiance exposure time. For example, apredetermined irradiance exposure time may correspond to a specifiedcure rate or curing time of a curing reaction at the target surface thatis to be driven by the irradiated light. As another example, irradiationuniformity may be enhanced to provide uniform irradiance above a minimumirradiance threshold.

If it is determined that irradiance uniformity is to be enhanced, method1500 continues at 1550, where the irradiance of middle portionlight-emitting elements of the one or more edge weighted linear arraylight sources may be boosted. For example, boosting may comprise one ormore of using higher intensity light-emitting elements (e.g., LEDs) inthe middle portion of edge weighted the linear array light sources,using lower intensity light-emitting elements in the end portions ofedge weighted the linear array light sources, integrating lens elementsor other optical elements with the linear array light-emitting elements,or supplying light-emitting elements individually with different drivecurrents. For example, boosting irradiance of the middle portionlight-emitting elements may comprise supplying additional drive currentto the middle portion light-emitting elements, or supplying lower drivecurrent to the end portion light-emitting elements. As another example,boosting irradiance of the middle portion light-emitting elements maycomprise lensing the middle portion light-emitting elements to collimateirradiated light therefrom and/or supplying additional drive current tothe middle portion light-emitting elements. Other methods andcombinations of boosting the irradiance of middle portion light-emittingelements may be used to enhance irradiance uniformity.

Next, method 1500 continues at 1560 where one or a plurality of edgeweighted linear array light sources are arranged side by side opposite atarget surface at a fixed plane. The distance of the fixed plane fromthe one or more light sources may be determined based on one or more of1520, 1530, 1540, and 1550 wherein arranging the target surface at thefixed plane opposite the one or more light sources can achieve uniformirradiance of the target surface.

Method 1500 continues at 1570 where power is supplied to the one orplurality of edge weighted linear array light sources to irradiate thetarget surface. Supplying power to the one or plurality of edge weightedlinear array light sources may include supplying additional drivecurrent to the middle portion light-emitting elements, or supplyinglower drive current to the end portion light-emitting elements in orderto enhance irradiance uniformity as in 1540 and 1550. Supplying power tothe one or plurality of edge weighted linear array light sources mayfurther comprise supplying power for a predetermined length of time oras prescribed by a controller control scheme. For example, one or morecontrollers (e.g., 1414) may supply power to the one or plurality ofedge weighted linear array light sources to irradiate the target surfaceaccording to a feedback control scheme. Other examples of controlschemes are described above in reference to FIG. 14. After 1570, method1500 ends.

In this manner, a method of irradiating light may comprise irradiatinglight from a linear array of light-emitting elements, the linear arrayof light-emitting elements aligned with and emitting light through acylindrical Fresnel lens, wherein the cylindrical Fresnel lens reducesthe angular spread of light in a widthwise axis of the linear array. Thelinear array of light-emitting elements may comprise a middle portion inbetween two end portions, the linear array having only a single row ofelements. The middle portion may comprise a plurality of light-emittingelements distributed over the middle portion with a first spacingthroughout the middle portions, and each of the end portions maycomprise a plurality of light-emitting elements distributed over the endportion with a second spacing throughout each end portion, wherein thefirst spacing is greater than the second spacing. A third spacingbetween the middle portion and each of the end portions may be greaterthan the second spacing and less than the first spacing.

Furthermore, the plurality of light-emitting elements in the middleportion may have a first irradiance, and the plurality of light-emittingelements in each end portion may have a second irradiance. Lightirradiated from the plurality of light-emitting elements distributedover the middle portion may have a first intensity, and light irradiatedfrom light-emitting elements distributed over the end portions may havea second intensity, wherein the first intensity is greater than thesecond intensity.

Further still, a first drive current may be supplied to each of theplurality of light-emitting elements in the middle portion, and a seconddrive current may be supplied to each of the plurality of light-emittingelements in the end portions, wherein the first drive current is greaterthan the second drive current, and the first irradiance is greater thanthe second irradiance.

Further still, the method may comprise one or more of reflecting,refracting, and diffracting light from each of the plurality oflight-emitting elements in the middle portion via optical elements,wherein each of the plurality of light-emitting elements in the middleportion comprises one of the optical elements, and wherein the firstirradiance is greater than the second irradiance. The method may furthercomprise one or more of reflecting, refracting, and diffracting lightfrom each of the plurality of light-emitting elements in the endportions via optical elements, wherein each of the plurality oflight-emitting elements in the end portions comprises one of the opticalelements, and wherein the first irradiance is greater than the secondirradiance.

It will be appreciated that the configurations disclosed herein areexemplary in nature, and that these specific embodiments are not to beconsidered in a limiting sense, because numerous variations arepossible. For example, the above embodiments can be applied toworkpieces such as inks, coated surfaces, adhesives, optical fibers,cables, and ribbons. Furthermore, the light sources and lighting systemsdescribed above may be integrated with existing manufacturing equipmentand are not designed for a specific type of light engine. As describedabove, any suitable light engine may be used such as a microwave-poweredlamp, LED's, LED arrays, and mercury arc lamps. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand subcombinations of the various configurations, and other features,functions, and/or properties disclosed herein.

Note that the example process flows described herein can be used withvarious lighting sources and lighting system configurations. The processflows described herein may represent one or more of any number ofprocessing strategies such as continuous, batch, semi-batch, andsemi-continuous processing, and the like. As such, various acts,operations, or functions illustrated may be performed in the sequenceillustrated, in parallel, or in some cases omitted. Likewise, the orderof processing is not necessarily called for to achieve the features andadvantages of the example embodiments described herein, but is providedfor ease of illustration and description. One or more of the illustratedacts or functions may be repeatedly performed depending on theparticular strategy being used. It will be appreciated that theconfigurations and routines disclosed herein are exemplary in nature,and that these specific embodiments are not to be considered in alimiting sense, because numerous variations are possible. The subjectmatter of the present disclosure includes all novel and non-obviouscombinations and subcombinations of the various systems andconfigurations, and other features, functions, and/or propertiesdisclosed herein.

The following claims particularly point out certain combinations andsubcombinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims are to be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and subcombinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. A light source, comprising: a cylindrical lens; a linear array oflight-emitting elements, the linear array aligned with and emittinglight through the cylindrical lens, wherein the cylindrical lens reducesan angular spread of light in a widthwise axis of the linear array, thelinear array spanning a lens length.
 2. The light source of claim 1,wherein the cylindrical lens is a cylindrical Fresnel lens having only asingle groove.
 3. The light source of claim 1, wherein the cylindricallens is a cylindrical Fresnel lens comprising a double cylindricalFresnel lens.
 4. The light source of claim 1, further comprising ahousing, wherein a window is mounted in a front plane of the housing,the window length spanning a front plane length, and wherein first andlast light-emitting elements of the linear array are positioned adjacentto widthwise edges of the window, and wherein window sidewalls at thewidthwise edges are aligned flush with housing sidewalls.
 5. The lightsource of claim 4, wherein the linear array of light-emitting elementsfurther comprises a middle portion in between two end portions, thelinear array having only a single row of elements, wherein: the middleportion comprises a plurality of light-emitting elements distributedover the middle portion with a first spacing throughout the middleportion; and each of the end portions comprise a plurality oflight-emitting elements distributed over the end portion with a secondspacing throughout each end portion, the first spacing greater than thesecond spacing.
 6. The light source of claim 5, wherein a third spacingbetween the middle portion and each of the end portions may be greaterthan the second spacing and less than the first spacing.
 7. The lightsource of claim 6, wherein: the plurality of light-emitting elements inthe middle portion have a first irradiance; the plurality oflight-emitting elements in each end portion have a second irradiance. 8.The light source of claim 7, wherein each of the plurality oflight-emitting elements in the middle portion comprises a higherintensity light-emitting element than each of the plurality oflight-emitting elements in the end portions, and wherein the firstirradiance is greater than the second irradiance.
 9. The light source ofclaim 7, wherein the plurality of light-emitting elements in the middleportion each comprises an optical element, the optical elementincreasing a first irradiance of its light-emitting element, and whereinthe first irradiance is greater than the second irradiance.
 10. Thelight source of claim 7, wherein the plurality of light-emittingelements in the end portions each comprises an optical element, theoptical element decreasing a second irradiance of its light-emittingelement, and wherein the first irradiance is greater than the secondirradiance.
 11. The light source of claim 7, wherein: the plurality oflight-emitting elements in the middle portion are supplied with a firstdrive current; the plurality of light-emitting elements in the endportions are supplied with a second drive current; and the first drivecurrent is greater than the second drive current.
 12. The light sourceof claim 4, wherein: the window comprises a front face and the windowsidewalls, the front face flush with the front plane, and the windowsidewalls extending perpendicularly back from the front plane.
 13. Amethod of irradiating light, comprising: irradiating light from a lineararray of light-emitting elements, the linear array of light-emittingelements aligned with and emitting light through a cylindrical Fresnellens, wherein the cylindrical Fresnel lens reduces an angular spread oflight in a widthwise axis of the linear array, the linear array oflight-emitting elements comprising a middle portion in between two endportions, the linear array having only a single row of elements,wherein: the middle portion comprises a plurality of light-emittingelements distributed over the middle portion with a first spacingthroughout the middle portions; each of the end portions comprise aplurality of light-emitting elements distributed over the end portionwith a second spacing throughout each end portion, the first spacing isgreater than the second spacing; a third spacing between the middleportion and each of the end portions is greater than the second spacingand less than the first spacing; the plurality of light-emittingelements in the middle portion have a first irradiance; and theplurality of light-emitting elements in each end portion have a secondirradiance.
 14. The method of claim 13, wherein irradiating light fromthe linear array of light-emitting elements further comprisesirradiating light from the plurality of light-emitting elementsdistributed over the middle portion having a first intensity, andirradiating light from light-emitting elements distributed over the endportions having a second intensity, wherein the first intensity isgreater than the second intensity.
 15. The method of claim 13, whereinirradiating light from the linear array of light-emitting elementsfurther comprises: supplying a first drive current to each of theplurality of light-emitting elements in the middle portion; andsupplying a second drive current to each of the plurality oflight-emitting elements in the end portions, wherein the first drivecurrent is greater than the second drive current, and the firstirradiance is greater than the second irradiance.
 16. The method ofclaim 13, further comprising one or more of reflecting, refracting, anddiffracting light from each of the plurality of light-emitting elementsin the middle portion via optical elements, wherein each of theplurality of light-emitting elements in the middle portion comprises oneof the optical elements, and wherein the first irradiance is greaterthan the second irradiance.
 17. The method of claim 13, furthercomprising one or more of reflecting, refracting, and diffracting lightfrom each of the plurality of light-emitting elements in the endportions via optical elements, wherein each of the plurality oflight-emitting elements in the end portions comprises one of the opticalelements, and wherein the first irradiance is greater than the secondirradiance.
 18. A lighting system comprising, a power supply; a coolingsubsystem; a light-emitting subsystem comprising, a housing; couplingoptics, wherein the coupling optics comprise a cylindrical Fresnel lens;a window mounted in a front plane of the housing; and a linear array oflight-emitting elements contained within the housing, the linear arrayaligned with and emitting light through the cylindrical Fresnel lens,wherein the cylindrical Fresnel lens reduces an angular spread of lightin a widthwise axis of the linear array, the linear array spanning alens length, wherein: first and last light-emitting elements of thelinear array are positioned adjacent to widthwise edges of the window,window sidewalls at the widthwise edges are aligned flush with housingsidewalls, the window sidewalls extending perpendicularly back from thefront plane, the linear array of light-emitting elements comprises amiddle portion in between two end portions, the linear array having onlya single row of elements, wherein: the middle portion comprises aplurality of light-emitting elements distributed over the middle portionwith a first spacing throughout the middle portion; and each of the endportions comprise a plurality of light-emitting elements distributedover the end portion with a second spacing throughout each end portion,the first spacing is greater than the second spacing; a controller,including instructions executable to irradiate light from thelight-emitting elements distributed over the middle portion having afirst irradiance, and to irradiate light from light-emitting elementsdistributed over the end portions having a second irradiance, whereinthe first irradiance is greater than the second irradiance.
 19. Thelighting system of claim 18, wherein the cylindrical Fresnel lenscomprises a cylindrical Fresnel lens having only a single groove. 20.The lighting system of claim 18, wherein the cylindrical Fresnel lenscomprises a double cylindrical Fresnel lens.